Polyolefin resins generally have many merits, for example, good productivity, excellent various molding properties, light weight, rust prevention and impact resistance so that they are widely used as materials for interior and exterior materials of cars, ships or the like, home electric appliances, household furniture, miscellaneous goods, construction materials etc. The polyolefin resins are non-polar and crystalline, unlike synthetic resins having a polarity, which are represented by polyurethane resins, polyamide resins, acrylic resins and polyester resins so that it is very difficult to apply on or bond to polyolefin resin molded articles by the use of common paints or adhesives.
On this account, in coating on or bonding to polyolefin resin molded articles, it has been conducted to improve adhesion to the surfaces of the articles by activating the surfaces.
For example, for car bumpers, the surface thereof has been subjected to etching treatment with halogen-containing organic solvents such as trichloroethane to enhance the adhesion between the surface and a coating film, or the surface has been subjected to pretreatment such as corona discharge treatment, plasma treatment or ozone treatment, and thereafter subjected to objective coating or bonding.
However, coating or bonding with conventionally known paints or adhesives not only takes large cost in the equipment but also requires a lot of time in the execution, and further results in uneven finish. This is the cause of inducing a difference in surface treated conditions.
In the above circumstances, as the paint compositions for improving the above problems, for example, JP-B-50-10916/1975 discloses a composition comprising modified chlorinated polyolefin as a main component, and JP-B-62-21027/1987 discloses a composition comprising a polyolefin modified with a maleic acid. These compositions, however, have insufficient adhesion strength to polyolefin resin molded articles so that they are usually only used to parts which do not need to have high adhesion strength.
Therefore, the advent of novel resin compositions and paint compositions capable of solving the conventional problems as described above has been desired.
The present inventors have earnestly studied for solving the above problems and found that the resin compositions prepared by mixing a resin solution containing a polyolefin or styrene thermoplastic elastomer with a photo-polymerization initiator are very useful. Thus, the present invention has been accomplished.
It is an object of the present invention to provide a novel resin composition capable of solving the conventional problems as described above.
Specifically, the resin composition of the present invention is prepared by mixing a resin solution containing a modified product of a thermoplastic resin (for example, a polyolefin or styrene thermoplastic elastomer) with a photo-polymerization initiator. The resin composition is applied on a substrate and irradiated with light, and then can be submitted to use as a primer, paint or adhesive.
The coating film of the resin composition according to the present invention has excellent adhesion to untreated polyolefin resin films or sheets, foamed or molded articles etc.